Saccharomyces cerevisiae Ribosomal Protein L26 Is Not Essential for Ribosome Assembly and Function

Abstract

Ribosomal proteins play important roles in ribosome biogenesis and function. Here, we study the evolutionarily conserved L26 in Saccharomyces cerevisiae, which assembles into pre-60S ribosomal particles in the nucle(ol)us. Yeast L26 is one of the many ribosomal proteins encoded by two functional genes. We have disrupted both genes; surprisingly, the growth of the resulting rpl26 null mutant is apparently identical to that of the isogenic wild-type strain. The absence of L26 minimally alters 60S ribosomal subunit biogenesis. Polysome analysis revealed the appearance of half-mers. Analysis of pre-rRNA processing indicated that L26 is mainly required to optimize 27S pre-rRNA maturation, without which the release of pre-60S particles from the nucle(ol)us is partially impaired. Ribosomes lacking L26 exhibit differential reactivity to dimethylsulfate in domain I of 25S/5.8S rRNAs but apparently are able to support translation in vivo with wild-type accuracy. The bacterial homologue of yeast L26, L24, is a primary rRNA binding protein required for 50S ribosomal subunit assembly in vitro and in vivo. Our results underscore potential differences between prokaryotic and eukaryotic ribosome assembly. We discuss the reasons why yeast L26 plays such an apparently nonessential role in the cell.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00539-12.

ACKNOWLEDGMENTS

We are grateful to all colleagues mentioned in the text for their gifts of material used in this study. We are indebted to A. Díaz-Quintana for his invaluable help with the analysis of the molecular structure of yeast L26 and related data. We also thank A. Fernández-Pevida for help during the in vivo translational assays, M. Carballo, L. Navarro, and C. Reyes of the Biology Service (CITIUS) from the University of Seville for help with the phosphorimager analysis, J. Talkish for advice about in vivo chemical probing, and J. Jakovljevic for critical reading of the manuscript.

This work was supported by grants from the National Science Foundation (MCB 0818534) to J. L.W. and the Spanish Ministry of Science and Innovation and ERDF (BFU2010-15690) and the Andalusian Government (CVI-271, P07-CVI-02623 and P08-CVI-03508) to J.C. R.B. is a recipient of an FPI fellowship from the Andalusian Government.